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A general approach to calculate the stiffness tensor of short-fiber composites using the fabric tensor determined by X-ray computed tomography
No full textIn this work, a general method to predict the stiffness tensor of short-fiber composites as a function of the fabric tensor (i.e. the tensor describing the architectural anisotropy of the micro-structure), determined by X-ray computed tomography, is presented. The proposed method does not depend on the type of fabric tensor used to characterize the symmetry properties of the composite. The experimental data used for method validation were obtained from thermoplastic composite matrices reinforced with short carbon and basalt fibers. The components of the stiffness tensor were calculated using the Mori-Tanaka model and the Halpin-Tsai equation for the stiffness of aligned short-fiber composites, but other micromechanics models could be used as well. The statistical alignment of the fibers in each portion of the sample was measured by determining the principal axes of the fabric tensor. The average properties calculated on sub-volumes provided moduli values in very good agreement with those determined experimentally. This approach is very general and easy to implement and does not need any numerical analysis tools
Environmental assessment of a spinning process for the production of ring-spun hybrid yarns from recycled carbon fiber: A cradle-to-gate approach
Get PDFThe study of sustainable remanufacturing processes using recycled carbon fiber to enhance its applicability in high-performance materials is a key research direction. To this end, their environmental performance should be assessed. Here, an attributional life cycle assessment combined with environmental life cycle costing is performed for an innovative spinning process recently developed for the production of ring-spun hybrid yarns suitable for manufacturing reinforcements for good-quality polymer composites. Results indicate that the process cumulatively affects approximately 65.4% of the total environmental impact regarding climate change, use of fossils, and use of minerals and metals. The preparing and carding phase predominantly contributes to nearly all environmental impact categories. Greenhouse gas emissions from the process were quantified as 10.5 kg-CO2 eq/kg, significantly below those produced by virgin carbon fiber manufacturing (24-31 kg-CO2 eq/kg). Overall, considering the potential landfilling or incineration of waste used as input, the process brings environmental benefits ranging from 56% to 76%. A sensitivity analysis indicates that replacing manufacturing scraps with recycled carbon fiber from pyrolysis represents the input change with the highest environmental impacts, while thermoplastic fiber use does not significantly alter environmental performance. The study demonstrates that using recycled carbon fiber from manufacturing scraps is preferable to using recycled carbon fiber from pyrolysis when life-cycle impact is considered. The choice between polyamide and polyester should rely on the specific impact category to be addressed and the desired mechanical properties to be achieved in the final composite
Realizzazione dell'impianto geotermico sperimentale a bassa entalpia presso il C.R. ENEA-Casaccia (Roma)
Get PDFQuesto Rapporto descrive le attività svolte nell’ambito del Piano Triennale di realizzazione 2019-2021 della Ricerca di Sistema Elettrico Nazionale, riguardanti la L.A. 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. Si pone, pertanto, in diretta continuità con il Rapporto tecnico “Studio preliminare di fattibilità e dimensionamento di massima di un impianto geotermico sperimentale a bassa entalpia integrato con pompa di calore” (RT/2023/2/ENEA). Nel corso del primo semestre del 2021 è stato realizzato il campo geosonde con l’installazione di sonde geotermiche verticali, a circuito chiuso e configurazione a doppia U, in quattro pozzi a diversa profondità ubicati nell’area adiacente l’edificio F40, all’interno del C.R. ENEA-Casaccia. Il pozzo 1 è stato realizzato a carotaggio continuo, fino alla profondità di 100 m, per ricavare e caratterizzare i litotipi lungo la successione stratigrafica. Le sonde geotermiche sono state installate soltanto fino a 70 m di profondità a causa di sgrottamenti delle sabbie a fondo foro. Sempre nel pozzo 1 è stato condotto il Ground Response Test per definire la temperatura indisturbata del terreno, la conducibilità termica media delle rocce e la resistenza termica delle sonde. Le perforazioni degli altri tre pozzi sono state eseguite a distruzione di nucleo. Contestualmente alla messa in posa delle sonde geotermiche, nei pozzi sono state inserite le fibre ottiche di tipo Distributed Temperature Sensor per acquisire la temperatura lungo l’intero pozzo con una risoluzione termica di 0,1 °C e una risoluzione spaziale di 2 metri. Inoltre, sono state definite le caratteristiche del circuito idraulico, in termini di portata distribuita tra le sonde e di perdite di carico distribuite e concentrate. È stato infine concepito lo schema funzionale tipo e redatto il computo metrico dell’impianto.This Report deals with the activities carried out in the framework of the 2019-2021 Three-Year Implementation Plan for National Electricity System Research, concerning line 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. It is, therefore, the follow-up to the technical report “Studio preliminare di fattibilità e dimensionamento di massima di un impianto geotermico sperimentale a bassa entalpia integrato con pompa di calore” (RT/2023/2/ENEA). During the first half of 2021, the borehole heat exchange field was realised with the installation of vertical closed-circuit geothermal probes, in a double-U configuration, in four boreholes at different depths located in the area adjacent to building F40, inside the C.R. ENEA-Casaccia. Well 1 was drilled with continuous coring to a depth of 100 m to extract and characterise the lithotypes along the stratigraphic succession. The geothermal probes were only installed up to a depth of 70 m due to the instability of the sands at the bottom of the hole. In well 1, the Ground Response Test was also performed to determine the undisturbed soil temperature, average rock thermal conductivity and thermal resistance of the probes. The drilling of the other three wells was performed at core destruction. Together with the installation of the geothermal probes, Distributed Temperature Sensor optical fibres were inserted in the wells to acquire the temperature along the entire well with a thermal resolution of 0.1 °C and a spatial resolution of 2 metres. Furthermore, the characteristics of the hydraulic circuit were defined, in terms of flow rate distributed between the probes, and distributed and concentrated pressure drops. Finally, the standard functional scheme was conceived, and the metric calculation of the system was drawn u
Design, Realization, and Test of Ultraviolet-C LED Arrays Suitable for Long-Lasting Irradiation of Biological Samples
Get PDFWe present the electrical and optical design, assembling, and thorough experimental characterization of two compact arrays of short-wavelength ultraviolet (UV-C) light-emitting di-odes (LEDs) suitable for near-field irradiation. Through a combination of technical expedients, we have achieved effective thermal management such that long-lasting irradiations are possible without appreciable deterioration of UV-C emission. We successfully used these compact UV-C LED arrays for long lasting irradiation tests aimed at generating the biosynthesis of defensive metabolites that enhance the resistance of plants and fruits to pathogen attacks. Finally, we comment on the possibility of implementing these compact UV-C sources on robotic systems to make an automated device suitable to reduce pesticide use in agricultural crops
Simulation and Detection of Structural Damage on Polymeric Materials Using a Terahertz Imaging System
No full textTHz radiation is able of penetrating most of the plastic materials, such as polytetrafluoroethylene (PTFE) and high density polyethylene (HDPE). The aim of this study will be to detect the presence of structural damage on polymeric materials by using a THz imaging system. Therefore, in this study this experimental system with its components will be described
Embrittlement of WCLL blanket and its fracture mechanical assessment
No full textIn the European fusion programme, the Water Cooled Lithium Lead breeding blanket (WCLL BB) uses EUROFER as a structural material cooled with water at temperatures between 295 °C-328 °C and a pressure of 155 bar. The WCLL BB will be significantly irradiated (>2 dpa), while some parts will not receive significant heat loads, e.g. the sidewalls or the back-supporting structures. The irradiation, together with the irradiation temperature of EUROFER below 350 °C, produces a shift of the ductile-to-brittle-transition temperature (DBTT) to levels above room temperature at neutron doses, causing material damage as low as 2-3 dpa. Even though the DBTT does not reach the operating temperature level, brittle/non-ductile fracture is a concern during in-vessel maintenance when the BB temperature is below the DBTT. Two loading scenarios were identified as severe in this respect: (i) re-pressurization of the WCLL BB cooling loop after in-vessel maintenance, and (ii) dead weight loads during lifting of the BB segment. The embrittlement of the WCLL BB was investigated by quantifying the local DBTT shift in its parts based on current knowledge of the embrittlement behaviour of EUROFER under neutron irradiation. Therefore, a suitable, not overly conservative procedure was derived considering dpa damage and transmuted helium effects. The results demonstrate the ability to identify the 3D spread of the severely embrittled zones in the structure whose impact on the structural integrity was assessed considering the risk of brittle/non-ductile fracture. Thereby, the fracture mechanics approach established in nuclear codes was applied assuming its applicability to EUROFER. The embrittled zones in the first wall (FW) and its sidewalls pass the criteria when assessing the relatively low stresses resulting from the coolant pressure. The assessment was then continued considering stresses appearing in the FW during maintenance, in particular, when lifting the BB segment and transporting it out of the vacuum vessel. In this context, the maximum tolerable flaw sizes were determined in a parameter study considering designs of the FW with different cooling channel wall thicknesses
Hemplime Blocks: Innovative Solution for Green Buildings in Italy
No full textIn the last years, the attention to an eco-friendly development of the building sector has increased the use of green materials, mainly because the construction sector is one of the most polluting. The hemplime block represents a valid option in this direction: it is a valuable product to improve the sustainability of the building. Like any new product, the main issues are given by the absence of specific rules, starting from the production phase until the installation. For this reason, the main objective of this work is to take a first step toward the long process of identifying possible guidelines for the production and the testing phase of the products to achieve a CE (European Commission) certification. Another essential aspect to clarify is the definition of indications for the laying phase of the prefabricated blocks. This study significantly contributes to reduce uncertainties and skepticism about this technology. With these objectives, some experimental tests have been carried out to verify the reliability of the data declared in the datasheets of hemplime blocks produced in Italy, justifying any incongruity. This study also investigates other aspects of hemplime block, such as the main pathologies that may affect this technology during its lifetime and the maintenance operations necessary to restore the product. Furthermore, the thermal performance of a wall was studied in a climatic chamber to study its behavior in conditions similar to service life
An Investigation on the Possible Application Areas of Low-Cost PM Sensors for Air Quality Monitoring
Get PDF: In recent years, the availability on the market of low-cost sensors (LCSs) and low-cost monitors (LCMs) for air quality monitoring has attracted the interest of scientists, communities, and professionals. Although the scientific community has raised concerns about their data quality, they are still considered a possible alternative to regulatory monitoring stations due to their cheapness, compactness, and lack of maintenance costs. Several studies have performed independent evaluations to investigate their performance, but a comparison of the results is difficult due to the different test conditions and metrics adopted. The U.S. Environmental Protection Agency (EPA) tried to provide a tool for assessing the possible uses of LCSs or LCMs by publishing guidelines to assign suitable application areas for each of them on the basis of the mean normalized bias (MNB) and coefficient of variance (CV) indicators. Until today, very few studies have analyzed LCS performance by referring to the EPA guidelines. This research aimed to understand the performance and the possible application areas of two PM sensor models (PMS5003 and SPS30) on the basis of the EPA guidelines. We computed the R2, RMSE, MAE, MNB, CV, and other performance indicators and found that the coefficient of determination (R2) ranged from 0.55 to 0.61, while the root mean squared error (RMSE) ranged from 11.02 μg/m3 to 12.09 μg/m3. Moreover, the application of a correction factor to include the humidity effect produced an improvement in the performance of the PMS5003 sensor models. We also found that, based on the MNB and CV values, the EPA guidelines assigned the SPS30 sensors to the "informal information about the presence of the pollutant" application area (Tier I), while PMS5003 sensors were assigned to the "supplemental monitoring of regulatory networks" area (Tier III). Although the usefulness of the EPA guidelines is acknowledged, it appears that improvements are necessary to increase their effectiveness
Worshop Ricerca, sviluppo e applicazioni per i Beni Culturali. Dai risultati del progetto VADUS alle future collaborazioni. Centro Ricerche ENEA Frascati 9-10 maggio 2023
No full textQuesto volume raccoglie le memorie del workshop “Ricerca, sviluppo e applicazioni per i Beni Culturali. Dai risultati del progetto VADUS alle future collaborazioni” che si è svolto a Frascati il 9 e il 10 maggio 2023 e rappresenta un ottimo strumento di divulgazione per i progetti e le attività in corso in ENEA sul tema della salvaguardia, tutela e cura del patrimonio culturale. Sono qui, quindi, presentate le soluzioni tecnologiche innovative, i prototipi high-tech e le infrastrutture di eccellenza che l’Agenzia mette a disposizione di musei, soprintendenze, istituzioni culturali e piccole e medie imprese per la diagnostica, la conservazione e la valorizzazione del patrimonio culturale e paesaggistico italiano. Con questo volume si vuole mettere a fattore comune il lavoro portato avanti da tutti i dipartimenti ENEA a beneficio sia del processo di comunicazione e collaborazione interna che dell’avvio di azioni sinergiche per affrontare nuove sfide e per la preparazione di nuovi percorsi progettuali competitivi da proporre a livello nazionale ed europeo. L’entusiastica partecipazione e il contributo di tutti i colleghi hanno permesso di arrivare al successo dell’evento e alla realizzazione di questo volume e, pertanto, a loro vanno i più sentiti ringraziamenti. Ai quali si aggiungono quelli rivolti ai numerosi ospiti e alle prestigiose istituzioni che sono intervenute alla discussione, avviando nuovi interessanti canali di comunicazione e collaborazione. Tra questi, il Museo Nazionale Etrusco di Villa Giulia, Il Museo Egizio di Torino, il Parco Archeologico di Ostia Antica, la Soprintendenza per la provincia di Viterbo e l’Etruria meridionale
Raman spectral mapping reveal molecular changes in cellulose aging induced by ultraviolet and extreme ultraviolet radiation
No full textIn the framework of a study on the aging phenomena of textiles we used Raman spectral mapping to analyze changes in the chemical bonds of cellulose of flax fabrics exposed to ultraviolet (UV) radiation in air, and extreme ultraviolet (EUV) radiation in vacuum. Our results show that both UV and EUV produce photolysis of cellulose bonds, which in turn triggers photochemical oxidation and dehydration, in a kind of “accelerated aging” and oxidative degradation of flax. In particular, we detected the formation of a large number of carboxyl and carbonyl groups, which, when conjugated, act as chromophores and give flax a yellowish hue. Remarkably, the mapping of Raman spectra makes it possible to identify the relative weights of molecular reactions responsible for the generation of oxidized groups and aging of cellulose. In particular, the comparison of spatially-resolved Raman spectra after irradiations UV in air and EUV in vacuum provides direct and quantitative evidence of the role of oxygen in the molecular changes leading to flax aging due to UV illumination. As an example, we found that atmospheric oxygen does not affect the change of the degree of polymerization of cellulose nor the formation of carboxyl and carboxyl groups. These results help to assess the possible benefit, if any, of preserving and exposing ancient cellulosic cloths in an inert, oxygen-free atmosphere